tvws:connecting unconnected
TRANSCRIPT
TVWS: Connecting unconnected
Gururaj Padaki | Jayaram Shanbhag
Saankhya Labs Pvt Ltd.
Agenda
Need for Rural connectivity
Rural Broadband: Available solutions and Issues
Requirement for Rural Broadband
TVWS for Rural Broadband
Brief overview to 802.22 standard
Q&A
Need for connectivity
We are more dependent on the Internet for communication, information, health services, education, disaster management and business relations
Internet has to be seen Basic Human Right in days to come
out of 7.2 billion world population only 3.3 billion populations is connected through internet
Out of 3.9 billion unconnected internet population 800million population is from INDIA – ideal case for make in INDIA and for INDIA
“10% increase in internet penetration can boost GDP by 1.4%”: ITU
Need for Rural connectivity
Connectivity is a MUST for rural area to manage limited resources and utilize them in a efficient way like power, irrigation etc.
Improves education and health services in rural area
E-commerce platform to connect end buyers to farmer – eliminating middle men
Rural Broadband : Available solutions and Issues
ADSL/Cable/Fiber
Mobile telephony(2G/3G and 4G)
Wi-Fi (IEEE 802.11a/b/g/n)
Wi-Max (IEEE 802.16)
Satellite
ADSL/Fiber/Cable
The most common type of broadband connection worldwide.
QoS you achieve relies heavily on how close your telephone exchange.
As rural areas are sparsely populated, service providers are unlikely to be interested as it wouldn’t be commercially viable.
Big challenge in Operation and Maintenance of cabling.
With cabling, need another 20years to cover remaining 3.9billion population.
Mobile telephony (3G and 4G)
This is one of the fast and scalable ways to connect rural area.
Involves costly wave spectrum
Unfortunately 3G/4G coverage in countries like INDIA is patchy, particularly in the rural areas.
High entry costs and poor ROIs currently doesn’t suit the growing countries like INDIA.
Wi-Fi (IEEE 802.11a/b/g/n)
Works with un- licensed band and cost effective CPE(Customer Premises Equipment) and AP(Access Point) for deployments.
Well suited for coverage up to 100-200meters.
Not suitable for sparsely populated rural area of 15-20kms.
Wi-Max (IEEE 802.16)
Mobile Wi-MAX was a replacement candidate for GSM and 3G technologies.
Wi-Max operates from 2 to 11 GHz licensed band and based on WRAN topology.
This is good candidate for last mile rural connectivity which is limited up to 2-3Kms due to its short multipath handling capability.
Satellite
Better alternative to cover bigger geography wirelessly.
Building, launching and operating satellites is very expensive which makes service to be costly.
High latency as signal have to travel 46000 miles from customer end to back haul gateway.
Needs line of site link and depends on weather conditions.
Comparison of different options
Standard Range (KMs)
Entry Cost
Frequency Band
Deployment time
Maintenance cost
Network latency
ADSL/Cable/Fiber
1-2 High NA High High Low
Mobile telephony
5(typical) High Licensed Medium Medium Low
Wi-Fi 0.1 Low Un-licensed
Low Low Low
Wi-Max 2-3 Medium Licensed Low Low Low
Satellite >100 High Licensed High Low High
Requirement for Rural Broadband
Entry Cost – Low like Wi-Fi
Range – at least 15-20Kms
Deployment time and Scalability – like Wi-Fi
Network Latency - <50msec
Speed per user – At least 1Mbps to have video call
Network Topology – WRAN
Characteristics of different WRAN standards
Rural Broadband – Who Fits the Bill
802.22b - Cognitive Wireless Regional Area Network(WRAN) Range – 30Kms
Network Topology – WRAN(Fixed installation),no mobility
Entry Cost – Less, uses un-licensed TVWS Band
What/Where is TVWS
TV Whitespace(TVWS) are unused gaps in TV broadcast spectrum (470-690MHz)
Where
TVWS Policy in place
USA, UK, Philippines, Singapore, Korea, South Africa
Under consideration/Trials
India, Indonesia, Vietnam, Japan
Malawi, Kenya, Botswana
Brazil, Argentina, Columbia
Kazakhstan
Why TVWS
Better Coverage than Wi-Fi • FSPL(dB)=20log10(d)+20log10(f)+
92.45 • FSPL free space path loss • d distance in KMs • f frequency in GHz
Long range with low power • Fewer towers Lower Capex • Runs off solar power Lower
Opex • Ideal for low user density areas
Better Non-Line-of-Sight (NLOS) Performance
Picture courtesy: Carlson wireless
Spectrum allocation in TVWS Band
TVWS Band allocation by taking existing licensed use Offer the promise of opportunistic access to under-utilized
frequency bands Location-aware wireless BS/CPE devices, assisted by
databases for band allocation
Overview – 802.22 Focus Area Rural Wireless broadband service
Core Technology Cognitive radio technology based un-licensed TVWS
Band without affecting incumbents Spectrum sensing, spectrum management, intra-
system co-existence, geo-location Mobility and Portability
Limited mobility support with NO hand-off
Network Topology –Point to Multi Point Max EIRP – 4W Cell Radius – up to 100KMs (with MAC support) Incumbent Protection – Sensing and Data base access
Overview – 802.22 Protocol Reference Model
Overview – 802.22 Frame Structure
TDD Frame structure support
Super Frame:160ms Frame:10ms
Each frame consists of downlink (DL) sub-frame, uplink (UL) sub-frame, and the Co-existence Beacon Protocol (CBP) burst
Lengths of DL and UL sub-frames can be adjusted
Self Co-existence Window: BS commands subscribers to send out CBPs for 802.22
Overview – 802.22 PHY Features
PHY Transport -OFDM as transport mechanism. OFDMA is used in the UL
Modulation-QPSK, 16-QAM and 64-QAM
Coding–Convolutional Code is Mandatory. Turbo, LDPC or Shortened Block Turbo Code are Optional but recommended.
Pilot Pattern -Each OFDM / OFDMA symbol is divided into sub-channels of 28 sub-carriers of which 4 are pilots.
Max Spectral Efficiency - 3.5 bits/s/Hz
Spectral Mask – As proposed by FCC
Overview – 802.22 MAC Features
Connection-oriented MAC, establishes connection IDs and service flows which are dynamically created
QoS – Various types of QoS services are supported (UGS,rtPS,nrtPS,BE). ARQ supported. Uni-cast, Multi-cast and broadcast services are supported.
Dynamic and adaptive scheduling of quiet periods to allow the system to balance QoS requirements of users with the need to quiet down the network to support spectrum sensing
Subscribers can alert the BS, the presence of incumbents in a number of ways
BS can ask one or more subscribers to move to another channel in a number of ways using Frame Control Header (FCH)or dedicated MAC messages
Overview – 802.22 Cognitive Features
comprises of Spectrum Sensing Function (SSF), the Geo location (GL) function, the Spectrum Manager/Spectrum Sensing Automaton (SM/SSA) and a dedicated security sub layer 2
Spectrum Sensing Function - observes the RF spectrum of a television channel for a set of signal types and reports the results of this observation. Present in both BS and CPE
Spectrum Manager- Responsible for spectrum availability information, channel selection, channel management, scheduling spectrum sensing operation, access to the database, enforcing IEEE 802.22 and regulatory domain policies. Present only at BS
Overview – 802.22 Field Deployment Scenario
Picture courtesy: http://ecee.colorado.edu/~ecen4242/802_22/general_info.html
Overview – 802.22 Field Deployment
Base station Installation
CPE Installation
